Differentiate Children Septic and Inflammatory Arthritis by Comparative Analysis

This a multicentric prospective study that compares biological fluids as synovial liquid and blood samples to find biomarkers that could distinguish septic arthritis and juvenile idiopathic arthritis. Prospectively, patients will be recruited under the age of 15 who are in care for septic or inflammatory arthritis at the University Hospitals of Montpellier, Lyon, Nimes and Toulouse. Patients should have an indication of blood and synovial as part of their management : Group A: acute juvenile arthritis with suspicion of bacterial infection, , confirmed on a bacteriological plan, either by culture of the articular liquid or by blood culture, or by molecular biology in the articular liquid. Group B: Idiopathic juvenile arthritis and control topics (Group C). In this project, the aim is to analyze all in all 50 articular liquids and serum of inflammatory arthritises (Group B), and 30 articular liquids and serum of infectious confirmed arthritises (Group A) which will require the inclusion about 50 possibly septic arthritis. The diagnosis of infectious arthritis is not immediate, he(it) is confirmed at the latest three weeks after the draining. So a group of control will be constituted. Group C: the blood of 20 healthy children matched by the age and at the sex in the groups A and B will be collected to analyze elements studied in the blood. * Inclusion criteria : Group A and group B: * Subject of more than 6 months and under age 15 years, * Presenting acute arthritis taken care in the University Hospitals of Montpellier, Nimes, Toulouse or Lyon, and requiring an articular puncture * Child benefiting from a social security system, * Collection of the consent of the legal parents/representatives, Group C: * Subject of more than 6 months and under age 15 include * Taken care in the University Hospital of Montpellier, and requiring a venous draining, * Child benefiting from a social security system, * Collection of the consent of the legal parents/representatives * Non inclusion criteria / Group A and group B: * Contraindication in an articular draining: platelet 50 000/mm3, pathologic hemostasis * Treatment by biological therapy, corticoids or other immunosuppressant treatment in the month preceding the articular draining, * antibiotic begun more than 24 hours before the inclusion. Group C: · * Patient achieves of an inflammatory chronic pathology * Patient having presented an infectious episode in the previous 8 days -Patients under immunosuppressor or anti-infective Methods of measure of assessment criteria Analysis will be done on blood samples and synovial liquid, that remains after sample collected for the management of their disease. The blood test and an synovial liquid draining will be realized at the subject. Before freezing, aliquots will be realized so that every analysis can benefit from a minimum volume: * Cellular analyses: will be only made in Montpellier and established by the set of collected cells (no necessary volume). * Proteomic, MiRNA analysis and cytokine dosing will been done in the second time. Statistical analysis will be done to individualize biomarkers.